March 5, 2024

TPO Roofing: Thermoplastic Polyolefin Roof Systems

Thermoplastic polyolefin (TPO) is a top contender in plastic roofing. Get the full lowdown on TPO.

Time to read:
5 Minutes
Written by
Nicholas Capobianco

Roofing isn’t something that can be treated as an afterthought. It’s one of the most important parts of any residential or commercial structure. A roof protects the integrity of everything underneath it. Unfortunately, choosing the right roofing system can be confusing, costly, and a general pain in the neck for those unfamiliar with the different products available.

Whether you're a veteran roofer, new to the industry, or a property owner, one roofing type you need to know about is TPO. This layered roofing system is popular with buyers who want a solid product that won’t need to be replaced any time soon.

In this blog, we're diving into the world of TPO roofing, including:

  • What it is
  • The different layers of these roofs
  • Installing a TPO roof
  • TPO FAQs

What is TPO roofing?

TPO stands for thermoplastic polyolefin. The single-ply roofing membrane material is most commonly used on commercial roofs or flat roofs. TPO is just one part of the entire roof system, as there are many layers to this type of roof.

The material is manufactured in super long rolls or sheets, between 10 - 20 feet wide. The sheets are shipped in rolls, and unrolled, cut, and installed on individual roofs. 

The layers of a TPO roofing system

Installation of a TPO roof involves seven basic layers that all serve an important function.

1. TPO membrane

This is always the outermost layer of the TPO roofing system. The heating and cooling process specified above is used to seal the seas, and create that protective barrier. TPO is sold in thicknesses of 44, 60, and 90 millimeters. The thicker the membrane, the longer it will last before requiring replacement or maintenance.

2. Bonding adhesive

There are two ways to attach the TPO membrane:

 Mechanical attachment: This is a cheaper method that uses fasteners to attach the membrane to the roofing deck along the seams. The membrane can be attached in lower temperatures, but the space between fasteners can shorten the life of the roof.

Since it’s not attached completely, strong winds can cause parts of the membrane system to blow and separate.  Hot air from inside the building may fill these spaces, creating pockets of damp that eventually lead to the growth of mildew in the insulation. Mechanical attachment also reduces energy efficiency. The decking may need to be rated for a heavier load to compensate for wind gusts. 

Full adhesion: This involves an all-over adhesive that’s placed on the membrane and the layer to which it’s being attached.Full adhesion is exactly what it sounds like. This method costs more, but it eliminates the problems that come when the membrane separates from its base.

It also increases energy efficiency, prevents sound pollution, and provides an air barrier. The only drawback to full adhesion is the adhesive’s sensitivity to temperatures under 40° F, which makes it difficult to install during the winter.

3. Quarter-inch cover board

A cover board is usually made out of gypsum and works better to reinforce the membrane than insulation alone. This layer gives the TPO membrane something solid to attach to, and improves the long-term integrity and strength of the roof. The cover board isn’t always necessary, but is highly recommended when the roof is going to be exposed to additional stress.

4. Insulation

The standard insulation is made out of polyisocyanurate board, and comes in varying thicknesses. Like the TPO membrane, the insulation board can be attached in a few different ways:

Mechanically attached: This involves using five fasteners per 4x8 board to secure the insulation in place.

Fully adhered: Full adhesion requires another layer of substrate underneath the insulation boards. For this kind of insulation, TPO membrane will be adhered directly to the insulation layer. So, the insulation will need to be secured using between eight and 32 fasteners per board. This is what holds everything together and provides a strong outer layer.

Mechanically attached and adhered: Newly-poured concrete may not yet be a sturdy foundation for the rest of the roof. When this happens, both attachment and adhesion together is often appropriate.

5. Vapor barrier

A vapor barrier is a layer that provides protection from inside air trying to escape through the roof. This layer is appropriate in areas with colder climates and can stop you from having to purchase a new roof sooner than you would like.

6. Underlayment

Like the cover board, an underlayment is usually made out of gypsum and acts as an extra layer under the insulation. This can improve the fire rating for buildings that require it, but isn’t necessarily essential to the TPO roofing system.

7. Metal roof deck

The metal roof deck is the corrugated metal that sits underneath the other layers. Think of it as your commercial roof in the nude. The roof deck provides the initial foundation for a TPO roofing system.


Is TPO roofing affordable?

One of the biggest advantages to this roofing system is the cost. TPO roofing costs come in at a lower price point than almost any other option while still being a great, reliable option.

Are these roofs durable?

TPO seam strengths are reported to be three to four times higher than EPDM roofing systems, at a cost-effective price.

Environmental friendliness of TPO roofs

Another added bonus to this type of roof is that it's a great option for environmentally conscious buildings: It has no added plasticizers, helps with sunlight reflection, and is resistant to UV radiation.

The actual roof is white, so it works to reflect sunlight, improving energy efficiency.

What maintenance is needed on TPO roofs?

These roofs don't require any pressure washing or constant maintenance. You will want to inspect the roof if you experience any major weather like hail storms. But other than that, they're pretty sustainable.

Are the seams secure on a TPO roof?

Because TPO is installed in sheets, there are long, large seams that can leak if not installed properly. With proper heat welding and application, T-joints, and installation by a professional roofer, this shouldn't be a problem.

When should you install TPO roofs?

The roof membrane is heat-sensitive and needs to be installed in certain conditions to be effective. The key is to choose a season that allows for the most wiggle room in scheduling. Areas like Toronto may be best off installing TPO roofing outside of the deep winter. but this doesn’t mean that the system is out of the question in cooler climes.

TPO: A popular commercial roof for a reason

This many-layered roofing system is a great option for large commercial buildings. It's cost-effective, affordable, and reliable. If you're considering a TPO roof, be sure to ask your roofer for their opinion. They'll be able to tell you what roof will work for your building.

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